PROJECT SUMMARY Despite a great body of research linking school absences with children?s academic achievement, surprisingly little is established about whether and how absences may be linked to children?s social-behavioral engagement and executive functioning. However, there are developmental concerns associated with missing school, such as increased alienation from peers and adults, engagement in current and future risky behaviors, and fewer long- term economic opportunities. These negative ramifications are even stronger for vulnerable populations. Our research will fill in these gaps in knowledge and be one of the first to use nationally representative data to assess the associations between school absenteeism and children?s social-behavior development and executive functioning during the elementary school years. Our proposal is significant because we will not only identify how absenteeism correlates to the development of these skills, but we will also determine: (a) which school and classroom policies and practices are linked with absenteeism; and (b) consider these associations across grade- levels. In doing so, the results from this proposal will provide greater insight on which possible targets should be considered to address developmental decline and social-behavioral risks. To this end, we address the following four research aims: Aim 1: Identify classroom and school policies and practices and family attributes that are associated with lower levels of absenteeism and behavioral engagement and executive functioning in kindergarten. Aim 2: Examine the associations between absenteeism and children?s behavioral engagement and executive functioning in kindergarten. Aim 3: Determine who is at greatest risk as a result of school absenteeism in kindergarten. Aim 4: Assess the extent to which the trends, correlates, and outcomes of school absences change between kindergarten and fifth grade. We rely on data from the Early Childhood Longitudinal Study, Kindergarten Class of 2010-2011. These data provide extensive information on various domains of children?s development as they progress through elementary school. A key advantage of these data will be the breadth of information on children, families, teachers, and schools, which will permit for more robust estimates, as we can control for confounders to an extent not possible previously. An additional advantage is that the sample includes a remarkably diverse group of children. Taken together, our effort to identify factors that shape children?s school absences and their social- behavior and executive functioning, particularly for vulnerable populations, means that our results can help policymakers target school policies and develop new initiatives to address this public health issue.